Fuel burner control system



May 14, 1940. D, 55665 FUEL BURNER CONTROL SYSTEM Filed Aug. 30, 1939 4Sheets-Sheet 1 Gttorncg May 14, 1940. D. BEGGS FUEL BURNER CONTROLSYSTEM Filed Aug. 50, 1959 4 Sheets-Sheet 3 (Ittorneg May 14, 1940. D.BEGGS FUEL BURNER CONTROL SYSTEM Filed Aug. 30, 1939 4 Sheets-Sheet 4Gttomcg Patented May 14, 1940 PATENT OFFICE FUEL BURNER CONTROL SYSTEMDon Beggs, Toledo, Ohio, assignor to Surface Combustion Corporation,Toledo, Ohio, a corporation of New York Application August 30, 1939,Serial No. 292,695

8 Claims.

The present invention has for its object to provide improvements in aburner control system wherein the flow of gas to a pilot for the mainburner is shut off each time a master control switch, such as a roomthermostat, operates to shut down the main burner. Known control systemsof the type indicated have embodied more or less complicated controlcircuits and it is therefore one of the more particular objects of theinvention to provide a control system which shall embody a minimumnumber of operating parts for effecting the desired sequence ofoperation. Other objects and the various features of novelty andinvention will more fully appear from the detailed description taken inconnection with the accompanying drawing wherein the preferred form ofthe invention is shown.

In the drawings:

Figs. 1 and 2 are more or less diagrammatic layouts of one and the sameimproved control system, the difference between the two views being thatin Fig. 1 the master control switch (room thermostat) is shown as of thesingle contact type whereas in Fig. 2 it is shown as of the doublecontact type.

Fig 3 is a modification of the control circuits shown in Fig. 1, and

Fig. 1A, 2A and 3A are simplified electrical diagrams of the controlcircuits shown in Figs. 1, 2 and 3, respectively.

In the drawings, I0 indicates a conventional type of gas burner whoseoperation is to be controlled; II the main gas supply valve for theburner, this valve being biased to closed position, and I2 an electricmotor for opening the valve, the motor being shown as comprising a rotorI2 and a winding I3. Arranged in igniting proximity to the main burneris a pilot burner I4 adapted to be lighted by any suitable electricigniter generally indicated at I5. The gas supply line to the pilot isprovided with a normally closed valve I6 which is adapted to be openedby a solenoid I'I. Arranged in a position to be heated by the pilot is athermostat I8 of any preferred type, the same being shown as abimetallic element.

The purpose of the pilot thermostat I8 is to actuate two switches I9 and20 operatively connected to the thermostat in any suitable manner thatwhen the thermostat I8 is cold, the switch 20 will be in engagement withits contact 20' and the switch I9 will be open with respect to itscontact I9. When the pilot thermostat is hot, the situation is just thereverse, that is to say, 5 the switch l9 will be in contact with itscontact I9 and the switch 20 will be open with respect to its contact20'. Moreover, the arrangement is such that the said switches are neverboth closed at one and the same time.

Although the pilot burner may be of any pre ferred typeit is preferablyof the type having a vertical orifice Ida in one of its sides forpropagating fiame from the igniter I5 to the upper main flame orifice Nband having another vertical orifice I40 in its opposite side forpropagating flame from the main flame orifice to the orifice Md whichfaces the thermostat .I8. The

principal advantage of a pilot of this type is that primary of which isindicated at 22.

Referring now more particularly to Fig. 1, 25 indicates a master switchfor controlling the operation of the control system. This switch willordinarily be a room thermostat of the single or double contact type,the single contact type being shown in Figs. 1 and 1A. When there is nocall of heat, said switch is out of engagement with its contact 26 whichis the terminal of the power line lead PI. 21 indicates the coil of arelay whose armature is indicated at 28. When the coil 2'! is energized,the armature 28 engages with contact point 29, it being noted that thecontact 29 is connected 40 to the master switch 25 by wire 30. Note alsothat the master switch 25 is connected to the pilot switch contact 20'by wire 3|.

The operation of the system shown in Fig. 1 is as follows: 45

The parts are shown in the deenergized position with the pilotthermostat I8 in the cold position. When the master switch 25 is movedto closed position, the relay coil 21 and the ignition transformer 22are simultaneously energized by a circuit which includes the power linelead PI, thermostat contact 26, wire 3|, pilot switch 20, wire 32,ignition transformer primary 22', wire 33, relay coil 21, and wire 34 tothe other power line lead P2.

solenoid This holding circuit includes the power line lead Pl,thermostat contact',26, wire 30, relay contact 29, armature 28,.wire 36,solenoid wire 33,'relay' coil 21, and wire 34 to the other power linelead P2. Gas isthus free to flow to the pilot and is lighted by thespark being produced at electrodes l5.

After the pilot has been burning for a sufilcient length of time toimpart a predetermined amount of heat to pilot thermostat l8, the pilotswitch 20 will be moved to open position with the result that .theignition transformer is deenergized. However, the relay coil 21 andpilot valve solenoid remain energized by means of the holding circuitwhich has been previously established.

The pilot continues to burn with the result that-the pilot thermostat Itwill, in due course of time, move pilot switch I9 into engagement withits contact IS. The closing of switch l9 establishes an operatingcircuit for the main valve motor l2 to open the main gas valve II. Thiscircuit includes power line lead Pl, thermostat contact 26, wire 30,relay contact 29, armature 28, wire 36, wire 31, motor winding |3, pilotswitch l9 and wire 35 to the other power line lead P2. The result isthat the main burner is now operating, it being remembered that thepilot is burning.

When the room thermostat or master switch 25 is opened, the flow of gasto both the pilot and main burners will automatically be shut off, andthe relay will open. The pilot cannot again be put in operation untilafter the pilot thermostat l8 has cooled sufiiciently to first openpilot switch I9 and then close pilot switch 20, it being'remembered thatthe initial energizatlon of the parts depends upon the closure of switch20. For this reason, the entire apparatus must completely recycle eachtime the power is interrupted, either by the opening of master switch 25or by momentary'power failure.

- Although the system disclosed inFigs. 1 and 1A shows a single-contactroom thermostat, the invention is equally well adapted to the use of adouble-contact room thermostat, as will be readily understood byreference to Figs. 2 and 2A.

In Fig. 2, the double contact thermostat comprises a set of movableblades 40 and 4| which are in engageable relation with a pair ofcontacts 40 and 4| respectively. When the thermostat moves tocall-for-heat position, the blade 40 will engage with its contact 40',the blade 4| later engaging with its contact 4 I When the thermostatmoves to no-call-for-heat position, the situation is just the reverse,that is, contact 4| is first to open, the contact 40' opening later. Thecontact relationship is usually such that there is a 2 F. or 3 F.temperature differential between the opening or closing of respectivecontacts, the blade 40 being made relatively flexible to allow fordifferential in movement. It will be understood that in call-for-heatposition, the blade 40 will be firmly engaged with contact 40' by thetime that .blade 4| engages with contact 4|.

2'! indicates the coil of a relay whose armature is indicated at 28.When the coil 21' is energized, the armature 28 engages with relay con-.tacts 44 and 44'.

When the relay coil 21 is thus energized, the armature 28 moves to closethe relay contact 28. The closing of, this contact establishes'a'holding circuit for the relay coil 21, this circuit also being theenergizing circuit for the pilot valve The operation of the arrangementshown in Fig. "2' islas follows: The'pa'rts are'shown in the deenergizedposition, the pilot thermostat I8 being in cold position, and contact40' of the room thermostat.

being closed. When the blade 4| of the room thermostat engages with itscontact 4|, the relay coil 21 and the ignition transformer 22 aresimultaneously energized by a circuit which includes the power line leadPl, thermostat contact 40', blade 40 to blade 4|, contact 4|, wire 3|,pilot switch 20, wire 32, ignition transformer primary 22', wire 33,relay coil 21' and wire 34 to the other power line lead P2. When therelay coil 21' is thus energized, the armature 28' moves to close relaycontacts 44 and 44'.

, The closing of relay contact 44 serves to transfer the power throughthe room thermostat directly to contact 40' and thus eliminate excessivearcing at contact 4|, it being remembered that contact 40' is firmlyclosed, whereas contact 4| is very lightly closed. The relay and theignition transformer are now energized by a circult including power linePl, thermostat contact 40', wire 30, relay contact 44, armature 23, wire45, wire 3|, etc., back to the other power line lead P2. It will benoted that the apparatus is now no longer under the control of roomthermostat contact 4|, this contact serving only to initially energizethe relay and ignition transformer.

The'closing of relay contact 44 establishes a holding circuit for therelay coil 21', this circuit also being the energizing circuit for thepilot valve solenoid This holding circuit includes power line lead Pl,thermostat contact 40', wire 30, relay contact 44, armature 28f, relaycontact 44",, Wire 36, solenoid l1, wire 33, relay coil 21' and wire 34to the other power line lead P2. The pilot switches l9 and 20 are causedto be actuated in the same manner as that described in connection withFig. l.

When the pilot thermostat l8 moves to close the pilot switch IS, an

operating circuit for the main valve motor I2 is established, thiscircuit including power line lead 5 tacts are an inherent source ofmechanical trouble, and it will be appreciated that the type of relaydescribed is one that is least susceptible to contact misalignment.

There are a number of safety features worth noting. First of all, itwill be remembered that the relay must be closed before gas can beadmitted to the pilot burner. The relay can be initially closed only bymeans of a circuit which includes the ignition transformer. Thus, if theignition transformer primary should become open-circuited, makingignition impossible, the

relay cannot be initially closed, with the result;

that the pilot'valve cannot be opened. This eliminates any explosionhazard due to unburned pilot gas. 1

. This invention also inherently gives protec tion against a shortcircuit in theignition trans- 75 former, which is a common source oftrouble. The ignition transformer is operated in series with the relay.The pilot valve is also operated in series with the relay, and inparallel with the ignition transformer, as will be noted particularly inFigs. 1A and 2A. If the ignition transformer should becomeshort-circuited, there will be an excessive voltage drop across therelay, with the result that the pilot valve will not receive normalvoltage and thus will not open.

If the pilot switches i9 and 20 are out of normal adjustment, such aswould be the case if the pilot thermostat l8 became warped so as toclose switch l9 when the thermostat is cold, it is impossible to admitgas to'either the pilot or main burner. As previously pointed out,whenever switch I9 is in closed position, switch 20 is always open.Inasmuch as the relay cannot be initially energized unless switch 2|) isclosed, the entire apparatus will be rendered nonoperative if the pilotswitches are out of adjustment. 7

In the event that there is a momentary gas failure while the main burneris operating, the main burner and pilot burner will both beextinguished. However, the pilot will automatically be relighted as soonas the pilot thermostat I8 has cooled sufliciently to close pilot switch20, the latter serving to energize the ignition transformer. In thisregard, it will be seen that the ignition transformer can never beenergized while the main gas valve is open, in view of the contactrelationship of the pilot switches l9 and y In Fig. 3 I have shown how acombined pilot valve solenoid and relay may be used in the presentcontrol system. The relay-comprises a core 50 which extends into theupper end of the pilot valve solenoid ll'. When the solenoid isenergized, the core 50 attracts the armature 28l which closes the relaycontact 29'. A'resistor is indicated at 53. The remainder of theapparatus shown in this arrangement is the same as that described inconnection with Fig. l. The mode of operation is as follows:

When the room thermostat or master switch 25 is closed, the ignitiontransformer 22 and solenoid l'l are initially energized by a circuitwhich includes power line lead PI, master switch contact 26, wire 3|,pilot switch 20, wire 32, lgnition transformer primary 22', wire 33,solenoid l1 and wire 34 to the other power line lead P2.

When the solenoid I1 is energized, gas is free to flow to the pilot, andthe. relay contact 29' is closed. The closing of contact 29' establishesa holding circuit for the solenoid II, this circuit including power linelead Pl, contact 26, wire 30, relay contact 29', armature 28I, resistor53, wire 33, solenoid I1, and wire 34 to power line lead P2. It will beremembered that after the pilot has been burning for a period of time,the pilot switch l9 will be moved to closed position, thus establishingan operating circuit for the main valve motor l2. This circuit includespower line lead Pl, contact 26, wire 30, relay contact 29', armature28l, wire 31, motor winding l3, Wire 38, pilot switch l9 and wire 35 topower line lead P2.

When the master switch contact 26 is opened, the entire apparatus isshut down and must completely recycle before gas can be again admittedto the main burner.

It will be noted that resistor 53 is in the hold- I ing circuit for thesolenoid l1. This resistor together with the relay switch serve as ashunt circuit across the ignition transformer 22 and pilot solenoid, l1serves the same shunting purpose as the resistor in Fig. 3A, as will beappreciated.

What is claimed is:

1. In apparatus of the class described, the combination of a pilotburner, a pilot burner valve, an electric motor for opening said valve,an electric igniter for said burner, a control relay having a'normallyopen switch, a master control switch, an energizing circuit for therelay independent of the pilot valve motorand including said-master Icontrol switch and igniter, a holding circuit for the relay independentof the igniter and including said master control switch, the relayswitch and the pilot valve motor.

2. In apparatus of the class described, the combination of a pilotburner, a pilot burner valve, an electric motor for opening said valve,an electric igniter for said burner, a control relay having a normallyopen switch, a master control switch, an energizing circuit for therelay independent of the pilot valve motor and including said mastercontrol switch and igniter, a holding circuit for the relay independentof the igniter and including said master control switch, the relayswitch and the pilot valve motor, a normally closed switch in saidenergizing circuit, and means dependent on flame at the pilot foropening the last named switch whereby to deenergize the igniter.

3. In apparatus of the class described, the combination of a pilotburner, a pilot burner valve, an electric motor for opening said valve,an electric igniter for said burner, a control relay having a normallyopen switch, a master control switch, an energizing circuit for therelay independent of the pilot valve motor and including said mastercontrol switch and igniter, a holding circuit for the relay independentof the igniter and including said master control switch, the relayswitch and the pilot valve motor, a main burner arranged to be lightedby the pilot burner, a main burner valve,. a motor for opening the mainburner valve, and an energizing circuit for the main burner motorcomprising the relay switch and the master control switch.

4. In apparatus of the class described, the combination of a pilotburner, a pilot burner valve, an electric motor for opening said valve,a main burner, a main burner valve, an electric motor for opening saidmain burner valve, an electric igniter for the pilot burner, a controlrelay having a normally open switch, an energizing circuit for saidigniter which includes said relay, an energizing circuit for the pilotvalve motor which includes said relay, an energizing circuit for themain valve motor which includes the relay pilot flame causes the saidswitch to open and thus deenergize the igniter, said means comprising ashunt circuit across said energizing circuit, said shunt circuitcomprising the relay switch and an electrical element having suflicientresistance as to permit a substantial part of the relay current to fiowthrough the igniter prior to the opening of the said normally closedswitch.

6. In apparatus of the class described, the combination of a pilotburner, a pilot burner valve, an electric motor for operating saidvalve, a normally open first switch, said motor being operative whenenergized to open said valve and to close said switch, an electricigniter for said burner, a normally closed second switch, meansdependent on flame at the pilot for opening the said second switch, anenergizing circuit for said motor comprising the igniter and the saidsecond switch, and means for maintaining said motor energized after thepilot flame causes the second switch to open, said means comprising ashunt circuit across said second switch and igniter, said shunt circuitcomprising the said first switch and a resistor having suflicientresistance as to permit a substantial part of the motor current to flowthrough the igniter prior to the opening of said second switch. v

7. In apparatus of the class described, the combination of a main burnerand a master control switch for controlling its operation, a main burnervalve, a motor for opening said valve, a

pilot burner for lighting the main burner, a pilot.

burner valve, a motor for opening the pilot burner valve, an electricigniter for lighting the pilot,

a) switch and the relay switch and the first pilot switch, said firstpilot switch being closed when said heat responsive means is hot, meansfor closing the relay switch whereby to place said main valve motorunder control of the first pilot switch comprising an energizing circuitfor the relay, said last named circuit including the igniter and themaster control switch and the second pilot switch, the second pilotswitch being closed when said heat responsive means is cold whereby therelay can be initially energized only after the pilot has been out for aperiod of time, the said pilot valve motor and said relay switch servingto provide a holding circuit for said relay.

8. In apparatus of the class described, the combination of a main burnerand a master control switch for controlling its operation, a main burnervalve, a motor for opening said valve, a pilot burner for lighting themain burner, an electric igniter for lighting the pilot, a normallyclosed switch, means responsive to heat from the pilot for opening saidswitch when the pilot is burning, a relay having a normally open relayswitch, an energizing circuit for the main valve motor including themaster control switch and the relay switch, means for closing the relayswitch whereby to place said main valve motor under control of saidmaster control switch, said means comprising an energizing circuit forthe relay including the master control switch and DON BEGGS.

